1. Field of the Invention
The invention relates to a fiber suitable for producing an advanced silky knitted or woven fabric with a scroopy handle, an excellent luster, a color depth, a bulkiness and a natural irregularity, and thick and thin along its axis and having specific grooves on the surface, and to a process for producing the same.
2. Description of the Prior Art
A variety of modified shaped fibers are obtainable by a process consisting of producing fibers or fabrics with a easily-soluble polymer located in the vicinity of the surface of a composite fiber comprised of two differently-soluble thermoplastic polymers and then dissolving out the easily-soluble thereof. For example the inventers proposed in Japanese Patent Laid-Open No. 93819/1980 that a modified shaped fiber with a large degree of shape modification is obtainable by dissolving out an easily-soluble polymer having a plurality of locations isolated by a relatively-insoluble polymer from a composite fiber. This fiber however exhibits glitter luster and decreased color depth, although a scroopy handle can be obtained and its knitted or woven fabric is faulty in that any of a bulkiness, a natural irregularity and other properties specific to advanced silky knitted and woven fabrics are not obtained.
Japanese Patent Laid-Open No. 53210/1981 also discloses that a modified shaped fiber is obtainable by dissolving out an easily-soluble polymer located at specific points in the vicinity of the surface. It however has similar faults.
Japanese Patent Laid-Open No. 112535/1981 proposes a fiber having more than six axially-continuous grooves with the widths of 0.1 to 4.mu., the depths of 2 to 10.mu. and a high water absorption property. It is also faulty in that its color depth is not good because of the deep grooves, and any of a bulkiness, a natural irregularity and other properties cannot be obtained.
Further the inventors proposed in Japanese Patent Laid-Open No. 5912/1982 and Japanese Patent Laid-Open No. 5921/1982 a thread having a scroopy handle, an excellent luster, and grooves on the surface. It is obtained with tapering recesses formed at the transverse cross-section by dissolving out an easily-soluble polymer located in the vicinity of the vertexes of its multi-lobal shape. However, when knitted or woven into a fabric, this yarn tends to show unsatisfactory bulkiness and a monotonous appearance characteristic of many synthetic fibers.
Silky synthetic fibers are aimed at attaining the same characteristics as silk itself. The fabrics of silk however differ considerably from the knitted and woven fabrics of ordinary modified shaped polyester multi-filament fibers in the degree of scroopy handle, bulkiness and irregularity. Its fabrics become bulky when spaces are formed among fibers by removing sericin in their production process while polyester multi-filament fibers successfully become bulky when a thermal-shrinkage mixed yarn is made. The latter's manufacturing process however is complicated and at a heavy cost. Further, silk fabrics have such an irregularity that so advanced an appearance as not attained by conventional synthetic fibers is presented because their multi-filament fibers have a random irregularity in thickness along their axes. According to the measurement by a method to be described later, they have the Uster Evenness values of 1 to 3% and 10 to 30 and 0 to 5 peaks every 50 m of the Uster Evenness values of 4 to 10% and above 10% respectively.
A number of processes have been proposed for giving an irregularity in thickness to polyester multi-filament yarns through their irregular draw. Most of them form clearly distinctive thick and thin sections along their axes and gives a clear difference of color shade when dyed. These material yarns for advanced knitted and woven fabrics are not always satisfactory because of their large Uster Evenness values of 5 to several ten %.
Japanese Patent Publication No. 7207/1976 discloses a polyester multi-filament fiber having more than three less-than-3 cm long dispersed undrawn sections every 10 cm thereof and the elongations of 35- 70%. It is however faulty in that it shows a considerable difference of physical properties, particularly of large Uster Evenness value, between the thick and thin sections because its low-speed spinning yarns are irregularly drawn and a considerable difference of color shade when dyed and are susceptible of the variation of the tension in their textile process because of their large elongations.
Further Japanese Patent Laid-Open No. 116819/1980 discloses a thick and thin yarn obtained by a process consisting of composite spinning a core component of polyethylene terephthalate and a sheath component of a mixture of polyethylene terephthalate and a ionic dyeable polyethylene terephthalate copolymer and drawing this composite fiber at a temperature less than 75.degree. C. This too is not satisfactory as a material of advanced silky knitted and woven fabrics because it is aimed at producing varied dyeability effects and at a clear difference of color shade between the thick and thin sections and cannot be provided with any excellent luster.
As described heretofore, prior arts have not succeeded in obtaining any material yarn capable of providing a scroopy handle, a crisp hand, a rustle, an excellent luster, a color depth, a bulkiness and natural irregularity specific to advanced silky knitted and woven fabrics at the same time.